Biomechanical and Clinical Evaluation of Rib Anchors Richard H. Gross, MD Research Professor, Clemson University Clemson-MUSC Bioengineering Consortium Charleston, SC Staff surgeon, Shriners Hospital, Greenville, SC Current status of managing pediatric kyphosis deformity Papers divided into 3 categories 1. We got this! Cobb angle, kyphosis, age, and body mass index did not seem to influence our complication rate (Sankar, Avecedo et al. 2010) Preoperative kyphosis 48 degrees (upper range of normal) in our study, we have determined statistically significant change by means of correction in in thoracic kyphosis(tk), between the preoperative and the early postoperative periods and between the preoperative and last followup periods (p<.05) in the patients treated with growing rod technique (Atici, Akman et al. 2014) Mean preop 53.6, 39.9 last followup 3/23 proximal junctional kypshosis There was a decrease in mean TK from 59 degrees preoperatively to 36 after index surgery with an increase at the latest followup to 51 degrees. (Shah, Karatas et al. 2014) but also The patient with hypokyphotic had 30 and 140 kyphosis preoperatively.the kyphosis had increased to 40 degrees postoperatively in the patient with 30 degrees kyphosis and measured 90 degrees at the last followup. The other patient had 140 degrees kyphosis preoperatively that increased to 190 degrees and measured 270 degrees at the last followup.????????????? 2. We got this?...i m not so sure
This study identified an increase of every 20 degrees in the thoracic kyphosis angle as another significant independent risk factor.addtitional study is needed to determine the effectiveness of pedicle screw foundations in GR surgery. (Watanabe, Uno et al. 2013) Implant complications were more common in hyperkyphotic (>40 degrees) patients and increased linearly with increasing kyphosis (Schroerlucke, Akbarnia et al. 2012) 3. We got this..i don t think so. (In 14 patients) At latest followup, total kyphosis ranged from 43 to 124 degrees and averaged 90.7 degrees. Total kyphosis ranged from 10 degrees to 138 initially and averaged 68.1 degrees (Reinker, Simmons et al. 2011) (In 10 patients with arthrogryposis) At final followup kyphosis was 62 degrees (8% correction). Six patients had proximal junctional kyphosis of > 45 degrees at last followup (Astur, Flynn et al. 2014) The present casa confirm the statement of Akbarnia and Emans that the VEPTR cannot control or even improve an upper thoracic kyphosis (Lattig, Taurman et al. 2012) Kontraindicikationene Schweriegende Kyphose >70 degrees nach Cobb Contraindications Hyperkyphosis >70 degrees according to Cobb Osteoporotic bone Children > 10 years(wimmer, Wallnoefer et al. 2010) PJK after VEPTR insertion can occur(4/68). Patients with preoperative hyperkyphosis may be at higher risk. PJK..can become progressive and severe enough to require complex interventions. In this small case series, patients were revised to growing rods. (Li, Gold et al. 2013) Osteoporosis- an overlooked variable A search for keywords osteoporosis and growing rods, and osteoporosis and VEPTR yielded 0 results. The VEPTR manual lists inadequate strength of bone as a contraindication
BMD has a close relationship with the stability of pedicle screws in vivo, and BME values below 0>674 suggest a potential increased risk of nonunion when pedicle screw fixation is performed in conjunction with PLIF. (Okuyama, Abe et al. 2001) Clinical uncertainty greatest clinical uncertainty included indications for spine-based and rib based proximal instrumentation anchors. The use of rib anchors compared with spinebased anchors was ranked highly for consideration in future clinical trials.(corona, Miller et al. 2013) What constitutes normal kyphosis in children? (Lots of definitions, a couple of samples) 20-50 degrees (Boseker, Moe et al. 2000) average 39.9 degrees in children 8-19(Ghandhari, Hesarikia et al. 2013) The Rib Construct 1. Pretty simple- Lumbar laminar hooks, downgoing on ribs 2-3, upgoing on 4-5(Gross 2012) Developed as product of desperation - 13 yo boy with VATER syndrome, delayed bone age, prior growing rods, rapid worsening of kyphoscoliosis, could not tolerate growing rods to pelvis, Risser casting ineffective, thoracic kyphosis 104 degrees, spine T score -5.4 2. Clinical results of the RC in patients with thoracic hyperkyphosis (> 70 degrees), the degree felt by Wimmer as a contraindication to VEPTR usage) 14 patients (7 syndromic, 4 neuromuscular, 3 congenital), age 4-21, with thoracic hyperkyphosis of 71-135 degrees (ave preop 107.8 degrees), underwent instrumentation with the RC for proximal fixation in Nablus, Palestine or Charleston, SC. 4 Charleston patients had T scores, all had osteoporosis, ranging from -2.7 to - 6.9, average -4.2.
Average follow-up for surgical patients was 44.4 mos, range 29-70 mos. Ave preop kyphosis was 107.8 degrees, postop 69.5. 2 patients died of unrelated causes, 5 had proximal loss of fixation, 2 delayed deep wound infections with removal of instrumentation, 1 replaced with salvaged result. In 2 patients with proximal fixation failure, salvage was not possible (osteoporosis) but even in these patients, the thoracic kyphosis was modestly improved. Biomechanics of thoracic kyphosis Consider center of body mass proximal to the kyphosis or proximal to the superior instrumented vertebral segment, AND the distance of that center to the apex of kyphosis, or to the superior instrumented vertebra to quantitate a force vector Mean failure when loading against the caudad aspect of the pedicle was statistically significant greater than for the cephalad pedicle(lehman, Helgeson et al. 2012) Biomechanical testing Biomechanical resistance of pedicle screw construct and rib construct to kyphotic pullout forces in 50 lb pigs. The pig has 15 ribs Pedicle screws placed T3and T4 Rib construct placed over ribs 3-6 VEPTRs were not available for study 6 porcine spines with pedicle screws all failed at a remarkably consistent deflection angle of 38 degrees 6 porcine spines with rib constructs no failures
Other considerations -alternative to VCR -role of scapula and shoulder protraction -coronal plane correction -kyphosis associated with spina bifida(ahmad 2013) Conclusion the RC is an attractive alternative to GR and VEPTR for management of difficult kyphotic spinal deformity References Ahmad, A. A. (2013). "Treatment of spinal deformity associated with myelomeningocele in young children with the use of the four-rib construct." J Pediatr Orthop B 22(6): 595-601. Astur, N., et al. (2014). "TheEfficacy of Rib-Based Distraction with VEPTR in the Treatment of EArly-Onset Scoliosis in Patients with Arthrogryposis." J Pediatr Orthop 34(8-13). Atici, Y., et al. (2014). "The effect of growing rod lengthening technique on the sagittal spinal and the spinopelvic parameters." Eur Spine J. Boseker, E. H., et al. (2000). "Determination of "Normal" Thoracic Kyphosis: A Roentgenographic Study of 121 "Normal" Children." J Pediatr Orthop 20: 796-798.
Corona, J., et al. (2013). "Evaluating the extent of clinical uncertainty among treatment options for patients with early-onset scoliosis." J Bone Joint Surg Am 95(10): e67. Ghandhari, H., et al. (2013). "Assessment of normal sagittal alignment of the spine and pelvis in children and adolescents." Biomed Res Int 2013: 842624. Lattig, F., et al. (2012). "Treatment of Early Onset Spinal Deformity (EOSD) with VEPTR: A Challenge for the Final Correction Spondylodesis: A Case Series." J Spinal Disord Tech. Lehman, R. A., Jr., et al. (2012). "What is the best way to optimize thoracic kyphosis correction? A micro-ct and biomechanical analysis of pedicle morphology and screw failure." Spine (Phila Pa 1976) 37(19): E1171-1176. Li, Y., et al. (2013). "Proximal Junctional Kyphosis After Vertical Expandable Prosthetic Titanium Rib Insertion." Spine Deformity 1(6): 425-433. Okuyama, K., et al. (2001). "Influence of beon mineral density of pedicle screw fixation: A study of pedicle screw fixation augmenting posterior lumbar interbody fusion in elderly patients." The Spine Journal 1: 402-407. Reinker, K., et al. (2011). "Can VEPTR((R)) control progression of early-onset kyphoscoliosis? A cohort study of VEPTR((R)) patients with severe kyphoscoliosis." Clin Orthop Relat Res 469(5): 1342-1348. Sankar, W. N., et al. (2010). "Comparison of Complications Among Growing Spinal Implants." Spine (Phila Pa 1976) 35(23): 2091-2096. Schroerlucke, S. R., et al. (2012). "How does thoracic kyphosis affect patient outcomes in growing rod surgery?" Spine (Phila Pa 1976) 37(15): 1303-1309. Shah, S. A., et al. (2014). "The effect of serial growing rod lengthening on the sagittal profile and pelvic parameters in early-onset scoliosis." Spine (Phila Pa 1976) 39(22): E1311-1317. Watanabe, K., et al. (2013). "Risk factors for complications associated with growing-rod surgery for early-onset scoliosis." Spine (Phila Pa 1976) 38(8): E464-468. Wimmer, C., et al. (2010). "[Operative treatment of scolioses with the VEPTR instrumentation]." Oper Orthop Traumatol 22(2): 123-136.